Wideband receivers are configured to provide filtering to most out-of-band blocker signals before any baseband amplification. Wideband receivers can employ passive mixers that immediately down-convert an input current to baseband. A transimpedance amplifier (TIA) then converts any baseband current in the receive band to voltage.
A received radio frequency (RF) signal may include an unwanted blocker signal at frequency fb, and a wanted signal at frequency fw, which may be Δfb greater than fb, e.g., fw=fb+αfb. However, these unwanted blocker signals experience some amplification around the RF band. This unnecessary amplification of unwanted blocker signals has potential to saturate the receiver, thus resulting in degradation of performance.
Additionally, the output of the TIA may have an unwanted signal that originates from harmonics of the wanted signal that experiences some amplification. Although the bandwidth around which these harmonics experience amplification can be very small, blocker signals located at these harmonic frequencies potentially cause the receiver to saturate, introducing distortion. For example, a receiver gain of 20× could potentially amplify a 1V blocker signal to 20V. This unnecessary amplification of blocker signals at the TIA output has potential to also saturate the receiver, thus resulting in further degradation of performance.